1. Field of the Invention
This invention relates to devices for printing a continuous web and more particularly to devices that print using ink-jet pens.
2. Background Information
Electronic inline printing and processing of a continuous web of paper has become ubiquitous in recent years for a variety of purposes and industries. Such industries include publishing and “print-on-demand,” direct mail marketing, billing and the like. Typically, a web is directed from a large stand-mounted roll to one or more high-speed (typically greater than 100 pages per minute) electronic printers that deposit and fuse toner to the web. The web is then directed to further processing units that variously print, emboss, cut, sort, stack and fold the web, among other possible processes.
It is often desirable to apply a color heading, logo, decoration or other device to the web either before or after the electronic printer has applied toner print. One technique for applying variable colored printing is to employ a color toner print engine. Such engines typically employ one or more individual toner sources that feed one or more image-transfer elements. The image transfer elements lay the toner onto the web and fuse it via heating. However, this approach uses expensive color toner and may be prone to speed and reliability limitations.
A more efficient and cost-effective technique to applying colored print is to employ a so-called “ink-jet” pen or “cartridge.” The ink jet cartridge defines an ink source contained within a unitary housing. The ink source is an impelled fluid that is dispensed as droplets at a print head located at the bottom end of the cartridge (also referred to as a pen) through a microscopic gridwork of nozzles that define the print pixels of the cartridge. The nozzles are individually addressed through a print controller so that they dispense ink at an appropriate time with respect to the movement of the printing media (paper, etc.).
In a conventional ink-jet printer, the nozzle grid is relatively small (less than one-inch square), and the printing media is driven through the printer at a rate that allows the cartridge(s) to traverse the width of the media on a motorized carriage so as to provide a print line of a given thickness. In general, the cartridge's inherent speed of ink deposition and the carriage speed both serve to limit the throughput rate of the print media. This throughput rate is typically significantly slower that 100 pages per minute. Hence, a conventional ink-jet printer with traversing head(s) is seldom suitable for providing color print to a high-speed moving web.
In addition, the internal ink supply of even the largest, commercial ink-jet cartridge is relatively small, requiring cartridges to be frequently replaced and/or manually refilled. The replenishment of ink/cartridges would, thus, prove inconvenient and time-consuming for a large production run—particularly where only a small number of cartridges on a traversing carriage are used.
Accordingly, it is highly desirable to provide a system and method for applying color print to a high-speed moving web that is efficient and low maintenance. This system and method should allow for large production runs without requiring replenishment and should allow variable printing across the entire width of a web without halting the feed of the web. The system and method should support printing in a large array of possible colors that may be combined on a single web when desired.